From d60ad8fe478e9f4cda3dbf7bd5b243cfa104cc3b Mon Sep 17 00:00:00 2001
From: JingMatrix <jingmatrix@gmail.com>
Date: Fri, 30 Jan 2026 18:16:13 +0100
Subject: [PATCH] Handle swapped attestation lists on certain Android 11
 devices (#108)

Observed an abnormal Keymaster attestation structure on certain Android 11 devices where the `softwareEnforced` and `teeEnforced` authorization lists were swapped in order. This is a deviation from the documented specification and the behavior seen on most devices.

This non-compliance caused parsing failures, as the code expected the `teeEnforced` list to be at a fixed index (7). On the affected devices, this index contained the `softwareEnforced` list, which critically lacks the `TAG_ROOT_OF_TRUST` needed for successful validation and patching.

This commit introduces a defensive normalization step to handle this device-specific anomaly gracefully:

1.  Before parsing, the code now inspects the ASN.1 sequence at the expected `softwareEnforced` index (6).
2.  It checks for the presence of the `TAG_ROOT_OF_TRUST`, which can only exist in the TEE-enforced list.
3.  If the tag is found, the code concludes the lists are swapped and corrects the `allFields` array in-place by swapping the elements at indices 6 and 7.

By normalizing the data structure at the beginning, the rest of the parsing and patching logic can proceed without modification, ensuring correct operation on both compliant and non-compliant devices.
---
 .../attestation/AttestationPatcher.kt         | 26 +++++++++++++++++++
 1 file changed, 26 insertions(+)

diff --git a/app/src/main/java/org/matrix/TEESimulator/attestation/AttestationPatcher.kt b/app/src/main/java/org/matrix/TEESimulator/attestation/AttestationPatcher.kt
index ec9fa20..ee7552c 100644
--- a/app/src/main/java/org/matrix/TEESimulator/attestation/AttestationPatcher.kt
+++ b/app/src/main/java/org/matrix/TEESimulator/attestation/AttestationPatcher.kt
@@ -216,11 +216,37 @@ object AttestationPatcher {
         }
     }
 
+    // Function to check if a given ASN1Sequence contains the Root of Trust tag.
+    private fun sequenceContainsRootOfTrust(seq: ASN1Encodable): Boolean {
+        if (seq !is ASN1Sequence) return false
+        return seq.any { element ->
+            (element as? ASN1TaggedObject)?.tagNo == AttestationConstants.TAG_ROOT_OF_TRUST
+        }
+    }
+
     /** Parses the critical components from an existing attestation extension. */
     private fun parseAttestationExtension(certHolder: X509CertificateHolder): ParsedAttestation? {
         val extension = certHolder.getExtension(ATTESTATION_OID) ?: return null
         val sequence = ASN1Sequence.getInstance(extension.extnValue.octets)
         val allFields = sequence.toArray()
+
+        // Check if the fields are in the wrong order and swap them if necessary.
+        val softwareEnforcedCandidate =
+            allFields[AttestationConstants.KEY_DESCRIPTION_SOFTWARE_ENFORCED_INDEX]
+        val teeEnforcedCandidate =
+            allFields[AttestationConstants.KEY_DESCRIPTION_TEE_ENFORCED_INDEX]
+        // The signature of a swapped order: the RoT is in the software list's position.
+        if (
+            sequenceContainsRootOfTrust(softwareEnforcedCandidate) &&
+                !sequenceContainsRootOfTrust(teeEnforcedCandidate)
+        ) {
+            // Swap the elements in the array to restore the standard order.
+            allFields[AttestationConstants.KEY_DESCRIPTION_SOFTWARE_ENFORCED_INDEX] =
+                teeEnforcedCandidate
+            allFields[AttestationConstants.KEY_DESCRIPTION_TEE_ENFORCED_INDEX] =
+                softwareEnforcedCandidate
+        }
+
         val teeEnforced =
             allFields[AttestationConstants.KEY_DESCRIPTION_TEE_ENFORCED_INDEX] as ASN1Sequence